Omni-directional inertial switch



Sept. 19, 1961 A. E. JOHNSON 3,001,039

OMNI-DIRECTIONAL INERTIAL SWITCH Filed Dec. 30, 1959 FIGJA. 26 2 L .3

FIG.2. H I? $304M 5 27 BY AORNEYS INVENTOR 42 a ARTHUR E. JOHNSON UniteThe invention described herein may be manufactured and used by or forthe Government of the United 'States of America for governmentalpurposes without the payment of any royalties-thereon or therefor.

This invention relates generaly to a switching device and moreparticularly to an omni-directiona'l inertial switch, i.e., a switchwhich is responsive to acceleration in any direction. a

'More specifically, this invention contemplates a single pole switchcontaining a plurality of resilient linger con- .tacts, the movement ofwhich is controlled ultimately by the intensity and direction of asudden acceleration or force applied thereto. The fingers are normallyheld ,in position by resilient retaining springs and 1a conductingshaft. The springs and the fingers normally maintain a number ofinertial members in predetermined initial positions. If the containershould suddenly accelerate ondecelerate the contact fingers may beactuated selecfively by at least one at the inertial members, engagingthe inner surface of the conductive outer shell of the container. typeofswitch .is particularlysuitable for use. as an impact ,detonatorin a.tuze oar missile. .It is not intended, however, to limit the utilityto], any pan -tioular type device.

Accordingly, an object of this inventionjis to providea new and improvedtypeofinertia:switch.

* Another object of this invention is to provide a new and improvedomnidirectional inertial switch.

Other objects and many of the attendant advantages of this inventionwill become apparent frorn the following detailed description whenconsideredin connection with the accompanying drawings wherein:

gates Ptent 2 caps by means of resilient springs 21 and '22,respectively. 'Inner spring seats 15, 16 are maintained at apredetermined position with respect "to the longitudinal axis byretaining rings 33 and 34, respectively, and collar 1'9 of shaft 1 4.Conductive finger contacts 23, 24 and 25,.

26 are fixed to outer spring seats 17 and 18 respectively, by somesuitable means. As shown on FIG. 2, there .arepreferably eight suchfingers, four mounted on each outer spring seat, however, any suitablenumber may be employed. An annular inertial member 27 is supported bythe finger contacts so that its inner circumference is. normallymaintained equidistant from collar 19. The longitudinal movement ofmember 27 is restrained by inner spring seats 1 5, 16. Thus, the switchcomprises three inertial members, spring seats 17, 18 as we'll asannular member 27. Members 17 and 18 are responsive to components orforce suddenly applied along the longitudinal axis, while annular member27 is responsive to components of force suddenly applied perpendicularto the longitudinal axis. Terminal 28, attached to conductive s'hatt l4and outer shell 11 are adapted tcibe connected to any suitableconductors. A suitable terminal post maybe mounted on shell ll. When theswitch is in the position illustrated in FIG. la, it is apparent that noelectrical current path exists between terminal 213 and conductive shell1i.

FIG. '11; illustrates the position of the finger contacts of the switchimmediately after a force in the direction FIG. 1a illustrates asectional view ofaswitchof the present invention in its normalposition;

FIG. lb illustrates the switch in its closed position immediately afterit has suddenly been accelerated in aa direction parallel to its axis 10illustrates the switch in :its closed position immediately after it hassheen suddenly accelerated :in a direction perpendicular -to its axis;

FIG. 1d illustrates the switch in "its closed :position immediatelyafter it has suddenly theen accelerated in a direction sneither,parallel nor perpendicular to its taxis;

rneans. The end caps or rings 12, 13 are made of some appropriatetypezofiinsrilatnr, such :as plastic. 'Gonducting shalt or rod likeelement 14.runs the length of the enclosure and is maintained parallelto and concentric with thetshll 1-1ibyretaining'fingsiil; 132,135 and13.6 andby 'holeslocated in "the center of the end caps. "The shaft 14thus forms the longitudinal axis ofthe switch container. Outer springseats 17, 18 are designed to slide along shaft 14 but are normallyretained against the end indicated by arrow .29 has been suddenlyapplied thereto. Outer spring seat orinertial member 17 is moved towardinner spring seat 16 compressing spring 21 and causing conductive fingercontacts 23, 24 to engage the inner contact surface of conductive shell11, 11. Thus, aconnection is made between terminal '28 and the innersurface on conductive shellby way of shaft I land fingers I23, .24. pathis opened as soon as the suddenly applied force is removed due to theresilient action of spring '21. Spring .22 spring seat 18 and inertialmember 27 are not afiectedby suddenaccelerations in thedirectionfindicated by arrow 2% and accordingly the positions of contactfingers 25 and 26 are maintained substantially constant. If a Jforce issuddenly applied in the opposite direction, contacts 23 and .24 willremain stationary, while con- .tacts25 and .26 will engage theconductive shell.

FIG. 1c illustrates the position of the finger contacts immediatelyafter asudden acceleration or force .is applied to the switch in thedirection indicated by arrow 37. Such a ,force causes inertial member 27to slide along .co'llar19 as shown .andresults .in .at leastone-of thecontact fingers 23, 2 25, or 26 engaging shell .11, .fingerf24being soillustrated. -.Since there isno movement of the springs .21, '22 or ofthe spring seats, .there will be noChangeIinflOngitudinal position ofany of the contact fingers. .If .the enclosure .is suddenly acceleratedin a direction opposite to that indicatedlby arrow 37, or is suddenlydecelerated in the direction of arrow 31, his apparent that @contactwould be made'by-finger 2'3 withthat portion of .the shell designated 11 in .lieu of finger .24 engaging shell per tionlil.

fFIG. 21d illustrates .the position of the finger contacts when suddenacceleration in the direction indicated by arrow .38 'isoccurring. Such.a force causes inertial mem- "ber27 to slide along collar 19 asindicated. .Also spring seat 1'7 partially compresses spring 21.vTheresultant forces produced by seat v1'7 and inertial .member27:causes contact finger Zeinto engagement withsshell .11. i

' IFIG. 2 Iis.a.completesectional view ofztheswitch rinrits normallyopen position taken along the line 2--2 of FIG. la. with respect toshell 11, inertial member 27 and central shaft "14 is illustratedtherein. Contact fingers 23, 24, 41

The true relationship of the contact fingers I and 42 are mounted onspring seat 17 in quadrature relationship while fingers 25, 26, 43 and44 are mounted on spring seat 18 in quadrature relationship. Annularinertial member. 27 is thus held in place by the contact'finger's but isfree to move radially if sufiicient force is applied normal to shell 11.As a result of this freedom of movement'member 27 may be considered afloating mass.

\A complete electrical circuit is thus made between terminal 28 andconductive shell 11 whenever a sudden acceleration or deceleration inany direction occurs to the enclosure carrying this novel switch. It isalso apparent that the circuit will be immediately reopened when theenclosure is at rest or is subjected to constant velocity. The switchmay be modified by changing the loading of springs 21. and 22 or thelength and/or cross sectional configuration of the various contacts.Also, the mass of the spring seats or of the inertia members may bevaried. In such a manner, the total sensitivity or the sensitivity inany particular direction may be changed as desired. If the switch is tobe responsive solely to forces along the longitudinal axis, as shown inFIG. 1b, inertial member 27 may be removed. However, if the switch is tobe responsive solely to forces perpendicular to the longitudinal axis,as shown in FIG. 10, springs 21, 22 may be removed and spring seats 17and 18 may be attached to end caps 12, 13 respectively.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachv ings. vIt is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced'otherwise than as specifically described.

What is claimed as new and desired to be secured by face selectively inaccordance with the intensity and said rod like element within saidhollow element and insulated therefrom, resilient means engaging saidrod like element and electrically connected thereto for making contactselectively with said surface, an inertial member disposed on said rodlike element, means for prevent- 7 ing longitudinal movement of saidinertial member with respect to said rod like means, said last namedmeans and said inertial member constituting a central member, a portionofsaid resilient means engaging said central member, a second means formaintaining said central member and a second portion of said resilientmeans apart, whereby said contact means engages said surface selectivelyin accordance with the intensity and direction of force suddenly appliedto said switch.

2. The apparatus of claim 1 wherein said second maintaining means isresilient, and said resilient means includes an inertial member.

3. The apparatus of claim 1 wherein said resilient means normallyengages said first means.

4. A normally open switch comprising a rigid hollow conducting elementhaving an inner contact surface, a rod like conducting element, a firstmeans for maintainingsaid rod like element within said hollow elementand insulated therefrom, a first inertial member slidable along said rodlike means and electrically connected thereto, a first resilient meansengaging said inertial member for making electrical contact selectivelybetween said surface and said rod. like element, a central memberdisposed on said red like member, means for preventing longitudinalmovement of said central member with respect to said rod like element, aportion of said contact means engaging said central member, a secondresilient means interposed between said central member and said firstinertial member, whereby said contact means engages said surrection of aforce suddenly applied to said switch.

5. The apparatus of claim 4 wherein said central mem-' ber includes asecond inertial member movable only in any perpendicular direction tothe axis of said rod like member.

6. The apparatus of claim 4 wherein said second resilient means isa'spring encircling said rod like element.

7. The apparatus of claim 6 wherein said spring means normally biasessaid first inertial member against said first means.

8. A normally open switch comprising a conductive cylindrical shell, aconductive shaft, means for maintaining said shaft axially alignedwithin'said shell and insulated therefrom, a plurality of resilientconductive fingers for making contact 'selectivelywith the inner surfaceof said shell, a first inertial member 'slideably disposed on saidshaft, said fingers being carried on said first inertial member,a'second inertial member, means for preventing longitudinal movement ofsaid second inertial member with. respect to said shaft,' said lastnamed means and said second inertial member constituting a centralmember disposed on said shaft, said fingers engaging said centralmember, spring means disposed on said shaft for initially maintainingsaid central portion and said first inertial member apart, whereby saidfingersengage said shell selectively in accordance with the intensityand direction of forcesuddenly applied to said switch.

9. A normally open omni-directional inertial switch comprisingconductiveshell, a conductive shaft, a pair of insulation rings attached to saidshell and disposedon opposite ends of said shaft for maintaining saidshaft centrally aligned within said shell, a plurality of spring seatsdisposed on said shaft, first and second of said spring seats beinginertial members slidable on said shaft and each carrying four resilientconductive fingers arranged in quadrature relationship, said fingersmaking contact selectively with the inner surface of said shell, anannue lar inertial member encircling said shaft and disposed between athird and fourth of said spring seats, said annular member and saidthird and fourth spring seats forming a central member, means to preventmovement of said central member alongsaid shaft, the distance betweensaid third and fourth-spring seats'being such as to prevent lateralmovement of said annular member with respect to said conductive shaft, afirst spring encircling said' shaft and disposed between said first andthird spring seats, a" second spring encircling said shaft and disposedbetween said second and fourth spring seats, said springs normallybiasing said first and second spring seats against each of saidrespective insulation rings, all of said fingers engaging said centralportion, whereby said fingers engage said shell in response to movementof any of said inertial members selectively in accordance with theintensity and direction of force suddenly applied to said switch.

'10; The switch of claim 9 wherein the outer radius of said centralportion is greater than the distance between the axis of said shaft andthe point where said fingers engage said first and second spring seats,thereby causing said fingers to form an acute angle with a'line parallelto said shaft. a

1-1. The switch of claim -10 wherein the inner radius of said annularmember is substantially greater than the radius ofthat portion of saidshaft enclosed therein.

References Citedin the file of this patent UNITED STATES PATENTS2,793,260 Ciosek May 21, 1957 2,851,554 Feng et a1. Sept. 9, 19 58

